World Naked Gardening Day
Naked Gardening Day sounds like something that could have been started in Missoula. I mean, if Missoulians love anything outside of beer, hunting and running, it's gardening and being naked.
Your official excuse to be naked outdoors is Saturday, May 7th, hopefully your fence is a tall one. This will be the 12th annual World Naked Gardening Day and the official website (NSFW!) encourages you to simply "get naked and do some gardening." They also suggest that you do this "inside your house, in your back yard, on a hiking trail, at a city park, or on the streets." There is that whole public indecency law, so I'd keep your weed pulling to your own back yard.
Give it a try, May 7th, and make sure to invite your significant other along, it could result in some literally dirty hanky panky.